//
// detail/resolver_service_base.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2022 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef ASIO_DETAIL_RESOLVER_SERVICE_BASE_HPP
#define ASIO_DETAIL_RESOLVER_SERVICE_BASE_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/detail/config.hpp"
#include "asio/error.hpp"
#include "asio/execution_context.hpp"
#include "asio/detail/mutex.hpp"
#include "asio/detail/noncopyable.hpp"
#include "asio/detail/resolve_op.hpp"
#include "asio/detail/socket_ops.hpp"
#include "asio/detail/socket_types.hpp"
#include "asio/detail/scoped_ptr.hpp"
#include "asio/detail/thread.hpp"

#if defined(ASIO_HAS_IOCP)
# include "asio/detail/win_iocp_io_context.hpp"
#else // defined(ASIO_HAS_IOCP)

# include "asio/detail/scheduler.hpp"

#endif // defined(ASIO_HAS_IOCP)

#include "asio/detail/push_options.hpp"

namespace asio {
    namespace detail {

        class resolver_service_base {
        public:
            // The implementation type of the resolver. A cancellation token is used to
            // indicate to the background thread that the operation has been cancelled.
            typedef socket_ops::shared_cancel_token_type implementation_type;

            // Constructor.
            ASIO_DECL resolver_service_base(execution_context &context);

            // Destructor.
            ASIO_DECL ~resolver_service_base();

            // Destroy all user-defined handler objects owned by the service.
            ASIO_DECL void base_shutdown();

            // Perform any fork-related housekeeping.
            ASIO_DECL void base_notify_fork(
                    execution_context::fork_event fork_ev);

            // Construct a new resolver implementation.
            ASIO_DECL void construct(implementation_type &impl);

            // Destroy a resolver implementation.
            ASIO_DECL void destroy(implementation_type &);

            // Move-construct a new resolver implementation.
            ASIO_DECL void move_construct(implementation_type &impl,
                                          implementation_type &other_impl);

            // Move-assign from another resolver implementation.
            ASIO_DECL void move_assign(implementation_type &impl,
                                       resolver_service_base &other_service,
                                       implementation_type &other_impl);

            // Move-construct a new timer implementation.
            void converting_move_construct(implementation_type &impl,
                                           resolver_service_base &, implementation_type &other_impl) {
                move_construct(impl, other_impl);
            }

            // Move-assign from another timer implementation.
            void converting_move_assign(implementation_type &impl,
                                        resolver_service_base &other_service,
                                        implementation_type &other_impl) {
                move_assign(impl, other_service, other_impl);
            }

            // Cancel pending asynchronous operations.
            ASIO_DECL void cancel(implementation_type &impl);

        protected:
            // Helper function to start an asynchronous resolve operation.
            ASIO_DECL void start_resolve_op(resolve_op *op);

#if !defined(ASIO_WINDOWS_RUNTIME)

            // Helper class to perform exception-safe cleanup of addrinfo objects.
            class auto_addrinfo
                    : private asio::detail::noncopyable {
            public:
                explicit auto_addrinfo(asio::detail::addrinfo_type *ai)
                        : ai_(ai) {
                }

                ~auto_addrinfo() {
                    if (ai_)
                        socket_ops::freeaddrinfo(ai_);
                }

                operator asio::detail::addrinfo_type *() {
                    return ai_;
                }

            private:
                asio::detail::addrinfo_type *ai_;
            };

#endif // !defined(ASIO_WINDOWS_RUNTIME)

            // Helper class to run the work scheduler in a thread.
            class work_scheduler_runner;

            // Start the work scheduler if it's not already running.
            ASIO_DECL void start_work_thread();

            // The scheduler implementation used to post completions.
#if defined(ASIO_HAS_IOCP)
            typedef class win_iocp_io_context scheduler_impl;
#else
            typedef class scheduler scheduler_impl;
#endif
            scheduler_impl &scheduler_;

        private:
            // Mutex to protect access to internal data.
            asio::detail::mutex mutex_;

            // Private scheduler used for performing asynchronous host resolution.
            asio::detail::scoped_ptr<scheduler_impl> work_scheduler_;

            // Thread used for running the work io_context's run loop.
            asio::detail::scoped_ptr<asio::detail::thread> work_thread_;
        };

    } // namespace detail
} // namespace asio

#include "asio/detail/pop_options.hpp"

#if defined(ASIO_HEADER_ONLY)
# include "asio/detail/impl/resolver_service_base.ipp"
#endif // defined(ASIO_HEADER_ONLY)

#endif // ASIO_DETAIL_RESOLVER_SERVICE_BASE_HPP
